时间分辨电子动量谱仪的研制及相关实验

发布时间：2018-08-10 16:37

【摘要】：物质的微观结构,特别是原子核的空间排布和电子的密度分布,决定了其物理和化学性质。对原子分子电子结构或者轨道波函数的认识,特别是和化学性质和化学反应相关的前线轨道,直接影响了人们对化学性质的认识和化学反应机理的了解。随着泵浦-探测技术的应用,人们已经开始迈入了电子结构实时演化探测的大门,在超快动力学的研究上取得了突出的成果。电子动量谱学是一种独特的研究原子分子电子结构的实验手段,可以获得分子轨道动量空间的电子密度分布,经过几十年的发展,在动量空间分子轨道成像方面显现出其非常独特的优越性。本论文的主要工作是将泵浦探测技术和电子动量谱学技术结合在一起研制一台纳秒时间分辨的电子动量谱仪,用来探测激发态分子在演化过程中电离能和电子动量分布随时间的演化,从而研究分子激发态动力学。谱仪己经设计搭建完毕,得到了初步的调试结果。此外在日本东北大学高桥研究组联合培养期间,用该组的时间分辨电子动量谱仪对甲苯分子单重态第一激发态S1(π,π*)进行了研究,得到了S1态的电离能谱和电子动量分布。论文另外一部分工作是对分子轨道电子动量分布的振动效应的研究。对乙醇和三甲撑氧分子的电子动量谱学研究表明某些轨道的电子动量分布受分子振动的影响很大,在传统和时间分辨的电子动量谱学研究中都需要仔细考虑包括振动效应在内的各种因素对轨道波函数的影响。论文的内容共分为六章,各章内容如下:第一章概述了超快动力学成像概念和相关实验技术、电子动量谱学的原理和谱仪的发展以及电子动量分布理论评估需要考虑的问题,并引出了发展时间分辨电子动量谱仪的想法;第二章介绍了时间分辨电子动量谱仪的设计,包括总体设计、光学系统、脉冲电子枪、能量分析器、探测器、电子学系统、供电系统和真空及磁屏蔽等。第三章展示了时间分辨电子动量谱仪的初步调试结果。第四章介绍了在日本东北大学联合培养期间用该组的时间分辨电子动量谱仪对甲苯分子S1(π,π*)激发态的研究结果。第五章介绍了电子动量谱学方法对乙醇分子构象的实验和理论研究,考虑振动效应后,实验测量的电子动量分布和平衡构型理论计算不符合的问题得到了很好的解决。第六章对三甲撑氧分子外价轨道电子动量分布的振动效应进行了详细研究,发现考虑振动效应后理论电子动量分布和实验符合的更好。最后是论文的总结和对时间分辨电子动量谱学未来工作的展望。
[Abstract]:The physical and chemical properties are determined by the microstructure of matter, especially the spatial distribution of nuclei and the density distribution of electrons. The understanding of electronic structure or orbital wave function of atoms and molecules, especially the frontier orbitals related to chemical properties and chemical reactions, directly affects the understanding of chemical properties and the mechanism of chemical reactions. With the application of pump-detection technology, people have begun to enter the door of real-time evolution detection of electronic structures, and have achieved outstanding results in the study of ultra-fast dynamics. Electron momentum spectroscopy is a unique experimental means to study the electronic structure of atoms and molecules. The electron density distribution in the molecular orbital momentum space can be obtained. The molecular orbital imaging in momentum space shows its unique advantages. The main work of this thesis is to develop a nanosecond time-resolved electron momentum spectrometer by combining pump detection and electron momentum spectroscopy. It is used to investigate the evolution of the ionization energy and the electron momentum distribution over time during the evolution of the excited state molecule, thus to study the molecular excited state dynamics. The spectrometer has been designed and built, and preliminary debugging results have been obtained. In addition, the first excited state S1 (蟺, 蟺 *) of toluene molecule was studied by time-resolved electron momentum spectrometer during the co-culture of Takahashi research group of Japan's Northeast University. The ionization energy spectrum and electron momentum distribution of S1 state were obtained. The other part of the thesis is to study the vibration effect of electron momentum distribution in molecular orbit. The electron momentum spectra of ethanol and trimethoxy molecules show that the electron momentum distribution of some orbitals is greatly affected by the molecular vibration. The influence of various factors, including vibration effect, on orbital wave function should be carefully considered in the traditional and time-resolved electron momentum spectroscopy. The content of the thesis is divided into six chapters. The contents of each chapter are as follows: the first chapter summarizes the concept of ultrafast dynamic imaging and related experimental techniques, the principle of electron momentum spectroscopy and the development of spectrometer, and the problems to be considered in the theoretical evaluation of electron momentum distribution. The second chapter introduces the design of time-resolved electron momentum spectrometer, including general design, optical system, pulse electron gun, energy analyzer, detector, electronic system. Power supply system and vacuum and magnetic shielding, etc. In chapter 3, the preliminary debugging results of time resolved electron momentum spectrometer are presented. In chapter 4, the results of the study on the excited states of toluene molecule S1 (蟺, 蟺 *) by using the time-resolved electron momentum spectrometer during the co-culture of the Northeastern University of Japan are introduced. In chapter 5, the experimental and theoretical study of ethanol conformation by electron momentum spectroscopy is introduced. After considering the vibration effect, the problem that the calculated electron momentum distribution and equilibrium configuration are not consistent with each other is well solved. In chapter 6, the vibration effect of the electron momentum distribution of trimethylene oxygen is studied in detail, and it is found that the theoretical electron momentum distribution is in better agreement with the experimental results after considering the vibration effect. Finally, the paper is summarized and the future work of time-resolved electron momentum spectroscopy is prospected.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TH74

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